The proportion is .
Apply cross product property: If , then ad = bc.
(Cross products)
Apply distributive property: .
(Multiply:
)
(Multiply:
)
Apply subtraction property of equality: Subtract 70 from each side
\ (Apply additive inverse property:
)
(Subtract:
)
(Subtract 90v from each side)
Apply commutative property of addition: a + b = b + a.
\ (Apply additive inverse property:
)
(Subtract:
)
Apply division property of equality: Divide each side by negative 50.
\ (Cancel common terms)
(Divide:
)
The value of .